Prevention of corrosion



PREVENTION OF CORROSION Donald E. Rapp, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application April 7, 1958 Serial No. 726,615

3 Claims. (Cl. 260-6525) The present invention relates to the prevention of the corrosion of metals by polychlorinated hydrocarbons.

. Various metals are attacked by the polychlorinated aliphatic hydrocarbon solvents which are employed in degreasing operations and the like. Many inhibitor compositions have been suggested and employed to control this corrosion. It has been found that aluminum metal presents the most diflicult corrosion problems and that control of corrosion of aluminum is the ultimate goal to be achieved.

It has been found that a mixture of nitromethane and 1,4-dioxane when employed in amounts as low as 0.1 percent by volume of solvent mixture will substantially inhibit the corrosive attack of the polychlorinated hydrocarbons on aluminum. These components of the new composition can be employed in amounts of from 95 to 5 percent by volume of nitromethane to 5 to 95 percent by volume of 1,4-dioxane. Good results have been obtained when the ratio of components is about 1 to 1 and .the composition is employed in amounts of from 0.1 to 3 percent by volume of the halogenated hydrocarbon solvent.

The following examples illustrate the present invention but are not to be construed as limiting.

Example 1 A 50 ml. portion of commercial methylene chloride containing one or more of the various impurities found in degreasing baths was heated at the reflux temperature until visual observation showed black spots and/or pits on and in a 28 aluminum strip suspended half in the liquid phase and half in the vapor phase of the refluxing solvent. The following table records the results of the visual observations:

Test solutions:

AMethylene chloride B-Methylene chloride plus 0.5 percent by volume of vinylidene chloride "ice C-Methylene chloride plus 1 gram of Fe O DMethylene chloride plus 0.5 percent by volume of vinylidene chloride plus 1 gram of Fe O Days to Example Test Solution First N 0. Visual Corrosion 1 A.- 26 2 B--- 8 (l-.. 5 4 D.-- 10 5 B Plus 3 percent by vol. 1,4-dioxane 99 6 D Plus 3 percent by vol 1-4-dioxane..- 89 7 B Plus 3 percent by vol mtromethaue... 90 8 D Plus 3 percent by vol. nitromethane... 98 9 D+1 percent by vol. 1,4-dioxane 1 percent nitromethane 216 Thus it is apparent that the combination of nitromethane and 1,4-diox'ane inhibits the corrosion of aluminum when subjected to chlorinated hydrocarbons up to at least 2 /2 times to 3 times as long as either compound alone when employed in equivalent amounts.

Hydrocarbon solvents which are inhibited in the same manner are, in general, any polychlorinated aliphatic hydrocarbon, such as'for example, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, tetrachloroethylene, chloroform and trichloroethylene.

I claim:

1. A polychlorinated aliphatic hydrocarbon corrosion inhibitor composition comprising a mixture of from 5 to percent by volume of nitromethane and from 95 to 5 percent by volume of 1,4-diox'ane, respectively.

2. A corrosion inhibitor for use with polychlorinated aliphatic hydrocarbons which comprises a mixture of from 5 to 95 percent by volume of nitromethane and from 95 to 5 percent by volume of 1,4-dioxane.

3. A corrosion inhibited polychlorinated hydrocarbon composition comprising a polychlorinated aliphatic hydrocarbon and from 0.1 to 3 percent by volume of a mixture consisting of .from 5 to 95 percent by volume of nitromethane and from 95 to 5 percent by volume of 1,4-dioxane, respectively. 

1. A POLYCHLORINATED ALIPHATIC HYDROCARBON CORROSION INHIBITOR COMPOSITION COMPRISING A MIXTURE OF FROM 5 TO 95 PERCENT BY VOLUME OF NITROMETHANE AND FROM 95 TO 5 PERCENT BY VOLUME OF 1,4-DIOXANE, RESPECTIVELY. 